1. Field of the Invention
The present invention relates to a process and a device for positioning warp yarns and to a weaving loom equipped with such a device.
2. Brief Discussion of the Related Art
In the domain of weaving looms of the Jacquard type, it is known to proceed with the levelling of the harness, i.e. with the adjustment, with respect to the frame of the weaving loom, of the position of the mails of the heddles in their direction of displacement in their substantially vertical reciprocating movement. The aim is to obtain a high-precision positioning of the warp yarns during weaving. In the known devices, such adjustment generally takes place in two steps:
when the harness is manufactured, the harness cords are adjusted manually and individually to the and required length; PA1 when the Jacquard mechanism is positioned on its bearing structure, the positioning of this mechanism is adjusted by acting manually on jacks, in order to adjust the height of the mails of the heddles. PA1 displacing at least one warp yarn by an of the actuator which is associated therewith; PA1 detecting the passage of the warp yarn into a predetermined position; PA1 selecting a value of a control parameter of the actuator upon passage of the yarn into the predetermined position; and PA1 using the selected value a control point for controlling the actuator.
Such manual adjustments are long, fastidious, expensive and always imprecise, and their quality can be influenced if the operator is tired or lacks concentration.
It is a particular object of the present invention to overcome these drawbacks by proposing a device for positioning the warp yarns, which may be used automatically, with a precision and a reproducibility greatly improved over the known techniques.